凝析气藏的液相伤害与防治

Study on damage and prevention of liquid phase in gas condensate reservoirs

液相伤害是凝析气藏产能下降的一个重要原因,它包括反凝析伤害和外来液、地层水的伤害。凝析气井开采过程中,当地层压力小于露点压力时,将在地层中发生反凝析现象,导致产气量下降,同时,外来液、地层水造成的"水锁"现象也致使气相渗透率明显降低。通过文献调研介绍了凝析气藏的反凝析和水锁现象对地层的污染,其伤害机理主要包括多孔介质吸附作用、多孔介质毛细凝聚作用、气体滑脱作用、液阻效应和毛管数效应等;并阐述了各种反凝析污染的评价方法及具体的防治措施,如对于单一的油相伤害可采用注气、注溶剂和注溶剂+气的复合段塞,对于反凝析和水锁双重伤害,可用注甲醇和注CO2混相来解除。

The damage of liquid phase is an important reason for deliverability decrease of gas condensate reservoirs ,which includes the retrograde condensation pollution and the damages from extraneous water and formation water. During the production of gas condensate reservoirs,as the formation pressure declines to dew point pressure,the retrograde condensation pollution would be happen ,and the gas production rate will be decreased. At the same time, the water block effect caused by the extraneous water and formation water will result in a breakdown of gas permeability. Through document retrieval,this paper introduces retrograde condensation and water block effect to the formation pollution. The mechanism consists of porous medium adsorption,the capillary condensation, gas slip effect,water block effect and boundary of capillarity. It also formulates many ways of evaluation and measures of prevention,such as we can inject gas,solvent,or gas plus solvent at the same time for single oil phase pollution,and for both retrograde condensation pollution and water block effect,we can use mixed-phase injection of methanol and carbon dioxide.